Particle size issues

The amount of hydrogen chloride captured as sodium chloride was proportional to square root of time and sodium diffusion coefficients in glass cullets calculated were 2.9 - 3.9xl0 m /s at 823K. Also, chlorine-firee char can be produced by steam decomposition, even though particle size issue remains. 

For reproducibility, a standard operating procedure should be adopted. Table 4.7 illustrates the reproducibility that can be attained using calibrated sieves. The data is taken from the certification report on reference materials of defined particle size issued by the Commission of the European Communities and refers to data generated by four laboratories with BCR 68. 

Distinct IR spectra for the two different crystal forms. 50 Quantitation of one form within the other was performed by the DR technique. Different mixing techniques and particle size issues were investigated in an effort to generate homogeneous calibration samples. Quantitation of one crystal from (low-melting) in an- 16... 

The preparation of tetracycline eye ointment can be problematic and it is preferable to use micronised active substance to overcome particle size issues, knowing at the same time that the raw material must comply with chemical purity specification. The microcrystaUine raw material as described in USP meets both requirements. Another way to solve the problem is the preparation of a semi-finished product using tetracycline base, dissolved in semisolid base which significantly reduces the decomposition rate [66, 128, 129]. 

National Institute of Standards and Technology (NIST). The NIST is the source of many of the standards used in chemical and physical analyses in the United States and throughout the world. The standards prepared and distributed by the NIST are used to caUbrate measurement systems and to provide a central basis for uniformity and accuracy of measurement. At present, over 1200 Standard Reference Materials (SRMs) are available and are described by the NIST (15). Included are many steels, nonferrous alloys, high purity metals, primary standards for use in volumetric analysis, microchemical standards, clinical laboratory standards, biological material certified for trace elements, environmental standards, trace element standards, ion-activity standards (for pH and ion-selective electrodes), freezing and melting point standards, colorimetry standards, optical standards, radioactivity standards, particle-size standards, and density standards. Certificates are issued with the standard reference materials showing values for the parameters that have been determined. 

Particle size distribution relating to gas cleaning is well understood in the industry. This section deals with general rules of thumb. Certain important issues not included in this section are flue gas desulfurization, flue gas denitrification, hazardous waste gas cleaning, waste incineration gas cleaning, and removal of CO2 from flue gas. All these topics have special requirements, which must be considered separately in the design process. 

A classical issue in transition-metal catalysis is the dependence of catalytic activity on changes in the particle size of the metal clusters in the nanosize region [14]. 

There are two EPARs for eyedrops. Specific issues considered for these include container composition and tamper evidence, the optimization of the formulation and manufacture, preservative and preservation issues, and justification for the use of nonterminal sterilization processes. Many of the points concerning active ingredients and excipients are similar to those discussed above. Changes in formulation during the development process (e.g., for carbomers or surfactants) are mentioned. Particle size controls for suspension products are discussed. 

As we have seen in the previous chapter, the apparent topography and corrugation of thin oxide films as imaged by STM may vary drastically as a function of the sample bias. This will of course play an important role in the determination of cluster sizes with STM, which will be discussed in the following section. The determination of the size of the metallic nanoparticles on oxide films is a crucial issue in the investigation of model catalysts since the reactivity of the particles may be closely related to their size. Therefore, the investigation of reactions on model catalysts calls for a precise determination of the particle size. If the sizes of the metal particles on an oxidic support are measured by STM, two different effects, which distort the size measurement, have to be taken into account. 

Exposure and Bioavailability Issues. Primary routes of exposure to lead are via inhalation and ingestion. Lead exposure occurs through inhalation of airborne lead particles with deposition rates in adults of 30%-50% depending on factors such as particle size and ventilation rate (EPA 1986). Once deposited in the lower respiratory tract, lead appears to be almost completely absorbed (Morrow et al. 1980). 

The particle size was below 50 nm (as determined by TEM image analysis), considerably smaller than that of the starting nanoemulsion, and showed a slight mean particle size increase and a broader size distribution with increasing O/S ratio, supporting the template effect of the nanoemulsion. The authors showed that these nanoparticles are interesting not only from a basic viewpoint but also for applications where safety and environmental concerns are important issues. 

Concerning the Fischer-Tropsch synthesis, carbon nanomaterials have already been successfully employed as catalyst support media on a laboratory scale. The main attention in literature has been paid so far to subjects such as the comparison of functionalization techniques,9-11 the influence of promoters on the catalytic performance,1 12 and the investigations of metal particle size effects7,8 as well as of metal-support interactions.14,15 However, research was focused on one nanomaterial type only in each of these studies. Yu et al.16 compared the performance of two different kinds of nanofibers (herringbones and platelets) in the Fischer-Tropsch synthesis. A direct comparison between nanotubes and nanofibers as catalyst support media has not yet been an issue of discussion in Fischer-Tropsch investigations. In addition, a comparison with commercially used FT catalysts has up to now not been published. 

Precisely owing to the continuum description of the dispersed phase, in Euler-Euler models, particle size is not an issue in relation to selecting grid cell size. Particle size only occurs in the constitutive relations used for modeling the phase interaction force and the dispersed-phase turbulent stresses. 

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